CVE-2019-17026Actively exploitedAdded to KEV 2021-11-03

Mozilla Firefox And Thunderbird Type Confusion Vulnerability

Mozilla, Firefox and Thunderbird

Description

Mozilla Firefox and Thunderbird contain a type confusion vulnerability due to incorrect alias information in the IonMonkey JIT compiler when setting array elements.

CVSS severity for this advisory hasn't been enriched from NVD yet, check back shortly.

EPSS, exploit probability

High

46.3%

estimated chance of real-world exploitation in the next 30 days, higher than 98.8% of every CVE FIRST.org scores

Refreshed 10/28/2026, via FIRST.org's EPSS model, not CVSS, this measures likelihood of exploitation, not how severe it would be.

Required action

Apply updates per vendor instructions.

CISA-recommended due date: 2022-05-03

CWE-843

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